A technique of providing a display apparatus itself with a coordinate input function instead of providing a coordinate pointing member such as a mouse is proposed. For example, a configuration having a pressure sensitive touch panel disposed on a surface of the display apparatus, and a configuration having an electromagnetic induction tablet disposed on a back of the display apparatus are known. In the pressure sensitive touch panel, two transparent flat plates on which transparent electrode patterns made of a transparent electrode material are formed are opposed to each other with a predetermined clearance between them. Only in a portion pressed by a finger or the like, the electrode patterns are brought into contact with each other. As a result, resistance values in the electrode patterns are changed, and coordinates of the portion pressed by the finger or the like are calculated. As for the electromagnetic induction tablet, a predetermined electromagnetic wave is output from a dedicated tablet disposed on the back of the display apparatus. When a dedicated pen having a resonance circuit approaches the surface of the display apparatus, an electromagnetic wave emitted from the resonance circuit in the dedicated pen is received by the tablet and coordinates of the position of the dedicated pen are calculated by using a predetermined method. Both the pressure sensor touch panel and the electromagnetic induction tablet are used in portable personal computers and portable telephones (see Japanese Patent Application Laid-Open Publication Nos. 8-254682 and 7-225371).
However, the conventional display apparatus having the coordinate input function is difficult to reduce in size and often heavy in weight. Furthermore, as compared with the ordinary display apparatus, the conventional display apparatus having the coordinate input function is considerably high in cost and complicated in structure. Therefore, there is a problem, such as fragileness, in maintenance. Furthermore, it is strongly demanded that false operation is not caused by various kinds of noise.